A Unified Codebook Structure for Various Antenna Configurations

In downlink frequency division duplex (FDD) systems, the benefits of multi-user (MU) MIMO highly rely on the accuracy of channel quantization based on a predefined codebook. Linear antenna array is widely deployed in realistic systems, including various configurations such as uniformly-spaced linear array (ULA) and cross-polarized linear array (CLA) with closely-spaced or widely-spaced antennas. In this paper, a unified codebook structure is proposed for all these antenna arrays, in a form of two-stage feedback. The average cell spectrum efficiency and cell-edge user spectrum efficiency of the proposed codebook are evaluated through system level simulation and compared to the system performance with long term evolution (LTE) Rel-8 codebook and discrete Fourier transform (DFT) codebook. Simulation results show that the proposed codebook significantly improves channel feedback efficiency as well as system performance.